How wide can the Localiser signal range actually be?

The Localiser signal range is designed to provide precise lateral guidance for aircraft during the approach phase of landing. The correct range for the Localiser beam width is typically between 3° to 6° wide. This allows for enough room for pilots to stay on course while approaching the runway, ensuring that they have adequate lateral guidance without being overly sensitive to minor deviations.

When approaching a precision approach, having a Localiser signal width within this range helps improve safety and accuracy during landings. A width of 3° to 6° strikes a balance between providing sufficient coverage for pilots to maintain their course and ensuring they remain precisely aligned with the runway centerline as they descend.

The other options either provide a beam width that is too narrow or too wide, which would not meet the operational requirements for safe landings based on instrument approaches. Thus, the Localiser signal's design standard ensures that it operates effectively within the 3° to 6° range to enhance navigational accuracy.